07 Hyundai Tucson ABS failure

So I have an 07 hyundai Tucson with
about 60,000 miles on it. The other day
my ABS module failed and locked up my
brakes. This was a diagonal brake failure.
I took it to the dealer the next day and
they assessed that the ABS module had
failed due to bad brake fluid. There was
also a leak in the rear of the master cylinder.
They quoted me an entire brake system
overhaul including the ABS modules.
This was not what I wanted to hear.
The BIG problem is that 9 days prior
to this brake failure I had brought my
car in to the local mechanic to do an
inspection. I was experiencing sideways
pulling at high speeds. They did their
inspection and were unable to replicate
the issue. They said they visually checked
the brake fluid stating it looked good an
was at the appropriate level. They took
a picture from the side of the resevoir
but not of the brake fluid color.
In the picture of the resevoir the fluid
looks darker than it should. They gave a
report stating that the car was in great
shape and needed only a minor alignment
adjustment. I had the work done and
9 days later my brakes locked up.

What do I do?